The back of Aric McKeown's van is cluttered with illegal yard signs and placards that he peeled off utility poles and other public property in Minneapolis.

His opponents are usually hard to find, because most businesses that leave such calling cards don't advertise their names on these so-called "snipe" signs. They simply describe their services -- whether it's "We Buy Houses" or "Snow Removal" -- and provide a phone number answered by a machine.

But McKeown's most recent battle brought him to SGT Peterson's, a fitness company that operates at two sites in the Twin Cities and hopes to open more by the end of the year. Company owner Tim Peterson, a former Air Force staff sergeant who leads "boot camps" offering military-style drills, said he had no idea he was breaking the law until the confrontation started.

Most big cities ban snipe signs, with fines for offenders ranging from $50 to $150. But a lack of enforcement in Minneapolis has given rise to people like McKeown, who sometimes call themselves "sign sharks."

City officials field about two dozen complaints about snipe signs from April to September, when such signs proliferate. The practice is specifically banned under a Minneapolis ordinance that dates to the 1960s and was amended as recently as 2007. But there are no penalties for the vast majority of offenders, according to Steve Poor, the city's zoning manager.

"The city attorney has ruled that we can't go after people who benefit from the advertising," Poor said.

The city can issue a fine only if it catches offenders in the act of putting up a sign, but that hasn't happened in years. Poor said his team of three zoning inspectors tries to remove signs in an area all at once to send a message to violators, but he said it is not a high priority. Poor said he encourages residents to remove unwanted signs themselves if they can safely do so.

In St. Paul, officials received 110 complaints about annoying signs last year, almost double the amount in previous years.

"If this is a problem in St. Paul, we just are not hearing about it from residents," said Angie Wiese, a St. Paul safety and inspections public information officer.

'Gnomes' at work?

McKeown, 31, works as a marketing operations analyst for an e-commerce company that manages online financial transactions for big companies such as Microsoft and Kodak. He spends his nights teaching improv theater. For a couple of hours each week, he goes on snipe hunts.

The battle with SGT Peterson's began in April, when McKeown found the company's red-and-white signs offering "personal training" stuck in the ground near the Walker Art Center.

McKeown sent a tweet to SGT Peterson's informing them he had found their signs. Then he sent a picture of the signs in a trash can.

In a tongue-in-check response, SGT Peterson's tweeted back, explaining that the company employs "gnomes living under the Hennepin Ave Bridge" who put up the company's "USDA approved, Biodegradeable, Non-polluting" signs.

That ignited a series of snarky exchanges, in which McKeown blasted the company's "illegal advertising." He later wrote about the company on his blog, calling the operators "jerks" for putting their "ugly signs" on public property.

In July, McKeown found seven more signs in south Minneapolis touting Peterson's boot camp, this time using a different web address. McKeown estimates he's taken down more than 35 of the company's signs.

Peterson acknowledged that his company put up the signs, but he told Whistleblower that he always takes them down if asked by a property owner.

"Like many small businesses, we have a very small marketing and advertising budget. That means we have to be creative in how we use every dollar," Peterson said in a written statement. "Our street advertising has been a great way for us to inspire the community to get moving."

In an interview, Peterson said that he felt heckled by McKeown's "slanderous accusations" and that he had been talking to lawyers and may pursue a lawsuit against McKeown.

"I'm very frustrated with this matter," Peterson said. "The information is not accurate and I've already invested hours of time in this."

However, Peterson agreed to stop using snipe signs after reading the city ordinance earlier this month.

"I did not know 100 percent till today that they were illegal," Peterson told Whistleblower on July 18. "We're not going to post an illegal sign again."

McKeown said he's a bit skeptical, since he first provided that information to Peterson three months ago.